1. Field of the Invention
This invention relates in general to fuses for protecting electric circuits and in particular to time-delay fuses and methods for their manufacture.
2. Description of the Prior Art
Time delay fuses are designed such that when current through them exceeds the rating of the fuse for a predetermined time, heat will in time be generated and conducted to a fusible plug. The heat causes the plug to soften and create an open circuit through the action of a spring connected to it at one end tending to pull the plug away from a connection in the fuse. The other end of the spring is attached to the body of the fuse. One example of such fuses is presented in U.S. Pat. No. 2,111,749 to Bussman issued Mar. 22, 1938 which shows a combined time-delay and ordinary high current fuse in both cartridge type and plug type configurations.
Another example of such fuses is presented in U.S. Pat. No. 2,210,036 to McEntee issued Aug. 6, 1940. Yet another example of such fuses is shown in U.S. Pat. No. 2,342,310 to Taylor. A disadvantage of such prior art fuses has been in the connection of the spring to the fuse body so as to maintain the connection of the spring to the body at a point within the cylindrical body. Such cylindrical bodies are typically constructed of brittle or non-malleable insulating materials such as thermosets, melamines, ceramics, glass epoxies and the like which are difficult to notch, bend or punch. The art has searched for a connection structure which may be economically manufactured using such materials.